The invention relates to an intake port configuration for an internal combustion engine, where the swirl of at least one intake flow entering the combustion chamber via an intake port controlled by an intake valve can be varied, two or more flow paths being associated with at least one intake port, which paths join in the valve region, and the flow rate in at least one of the two flow paths being variable by means of a control element, and the two flow paths being formed by two completely separate intake passages, i.e., a primary passage and a secondary passage, which primary passage has a helical form.
In EP 0 258 207 B1 an intake port for internal combustion engines is described, which is provided with a dividing wall extending in longitudinal direction. In order to achieve a strong swirl flow in the cylinder under part-load conditions and obtain optimum filling of the cylinder at high engine speeds, the dividing wall is located in an intake port parallel to the cylinder axis, which on its own produces a very low swirl level. If a swirl flow is desired one portion of the port is closed by a control flap. As a consequence the flow of charge through the valve into the cylinder will be unsymmetrical, and a strong rotational flow will result by the interaction between charge and cylinder wall. The disadvantage of this design is that due to the basically neutral shape of the port the possible range will cover only low to medium swirl levels.
In AT 003 137 U1 an internal combustion engine with two intake valves per cylinder is disclosed, each of which is provided with an intake port. One of the two intake ports is divided into two passages by means of a partitioning wall extending over the entire port height. Once again the swirl level can be adjusted within a relatively narrow range only.
From EP 0 235 288 A1 an intake port configuration of the type mentioned in the initial paragraph is known. The secondary passage is configured as a swirl flow passage entering the helix of the primary passage against the flow direction of the latter which is configured as a helical passage. The disadvantage of this design is that the flow rate is significantly reduced when the swirl flow is deactivated compared to a fixed swirl pattern.
The demand for a variable swirl control in an internal combustion engine is thus characterized by an innate conflict of purpose, between a maximum control range within which the swirl flow should be adjustable and a maximum flow rate at a high swirl level.
It is the object of the present invention to avoid the above disadvantages and to develop an intake port configuration which will permit a high flow rate at a high swirl level, and a wide range of adjustment for the swirl flow.
In accordance with the invention this object is achieved by providing that the axis of the intake valve intersects or is tangent to the secondary passage at least at one point. The secondary passage may be designed as neutral passage or tangential passage, or it may assume various intermediate forms between the two extremes. In a preferred variant the secondary passage opens into the valve region in the direction of the intake valve axis, the axis of the secondary passage preferably coinciding with the axis of the intake valve in the valve region. The two intake passages thus lead to a single intake valve, the primary passage winding helically around the valve guide lug, whereas the secondary passage leads directly into the region of the valve guide lug of the primary passage, essentially concentrically with the intake valve axis.
The cross-sections of primary and secondary passages may be substantially equal according to a variant of the invention. This design has the advantage that the swirl motion will be adjustable over a very wide range, whilst a satisfactory flow rate will be obtained for both high and low swirl levels.
For adjusting the swirl level the control element should preferably be positioned in the secondary passage. In addition, it may be also provided that the flow rate in the primary passage be adjusted by a control element.
The control element may be configured as a flap, slide valve, cylindrical valve or the like, and the secondary passage and/or primary passage may be at least partially closed by the control element according to a preferred version.
In an especially preferred variant of the invention the proposal is put forward that primary passage and secondary passage have separate flange faces, the flange face of the secondary passage preferably being displaced relative to the flange face of the primary passage. The advantage of this arrangement is that in the instance of a flap-type control element the flap axis will not extend through the cross-section of the primary passage.
Primary and secondary passages start from the same side or different sides of the cylinder head. In an alternative configuration for a different set of boundary conditions at the cylinder head the primary passage at least will start from the top of the cylinder head. The primary passage runs essentially in the direction of the axis of the intake valve.
In a particularly preferable variant of a system with high swirl level it is provided that the flange face of the primary passage and the flange face of the secondary passage are located in different planes preferably subtending an angle of about 90xc2x0.
In further development of the invention it is proposed that a flow guide rib be provided in the region of the valve guide lug as an extension of a partitioning wall between primary passage and secondary passage, which flow guide rib is open towards the intake port, the height of said rib preferably decreasing in flow direction, and the flow guide rib at least partially following the helical form of the primary passage in an especially preferred version. The flow guide rib formed at the intersection of the two individual passages will have its impact on the flow characteristic of the intake flow arriving at the combustion chamber. Compared to previously known intake port configurations with passages formed by a partitioning wall, the design of the flow guide rib will permit more variation.
The intake port configuration may be employed with internal combustion engines with one, two, or more intake valves per cylinder. In intake systems with a plurality of valves the partitioning of the intake port will considerably improve the flow rate at a high swirl level, compared with conventional shut-off systems.
In further development of the invention it is proposed that a fuel injection device for individual fuel injection enter at least one intake passage, i.e., preferably the secondary passage. To prevent fuel from being deposited at the wall of the helical end of the passage, which would considerably increase emissions and fuel consumption, it is proposed in a preferred variant of the invention that the fuel jet delivered from the fuel injection device be directed onto the valve head of the intake valve. The fuel is thus injected into the secondary passage and is transported swirl-free by the secondary air stream into the valve region of the helical passage, the flow being directed against the valve head. Since the fuel stream is enveloped by secondary air no fuel droplets will settle on the wall of the helical end of the passage.
In order to promote fuel concentration at the central passage area it is proposed that the axis of the fuel jet subtend an angle of 0xc2x0 to 45xc2x0 with the intake valve axis, the axis of the fuel jet preferably intersecting the axis of the intake valve in the area of the valve head.
In yet another advantageous variant of the invention the proposal is put forward that the secondary passage, which is entered by the fuel injection device, should end in the area of the valve head in the immediate vicinity of the valve stem. The fuel is thus injected directly into the valve region in the direction of the valve head. The secondary passage, which may advantageously be formed by a pipe inserted into the valve region, will protect the fuel stream against the intake flow of the helical passage and will prevent fuel particles from being swept along with the swirl flow and carried towards the wall of the helical end of the passage.